Epithelial cells lining the gastrointestinal tract are the front line of defense against commensally and potential pathogenic microbes. In accordance with this role, upon microbial breach of the intestinal epithelium, these cells activate expression of genes that promote an innate immune inflammatory response and subsequent regulation of adaptive immune immunity. My sponsor has demonstrated that a primary means by which intestinal epithelial cells detect microbes is toll-like receptor 5 (TLR5)-mediated detection of bacterial flagellin. Since TLR5 recognizes flagellins from commensally and pathogenic microbes, the biology of TLR5 is likely germane to understanding both innate immunity and diseases characterized by dysregulated mucosal immunity toward commensally microbes such inflammatory bowel disease. Little is known about TLR5 signaling beyond my sponsor's demonstration that it, but not any other TLRs, confer NF-kappaB-mediated gene expression in response to flagellin. While many pro-inflammatory agonists activate NF-kappaB, emerging studies by my sponsor, his collaborators, and others indicate that there are distinct differences in the overall patterns of gene expression induced by different proinflammatory agonists. This proposal investigates the hypothesis that TLR5 activates a specific pattern of signal transduction events that mediate flagellin-induced changes in epithelial gene expression. Specifically, I propose to examine the role of MAP kinases, Ca++-mobilization, and STAT activation in regulated TLR5-mediated gene expression in gut epithelia.